Sumner, W. G., & Keller, A. G. (1914). The challenge of facts: And other essays. Yale University Press; [etc., etc.].
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रSumner, William Graham, और Albert Galloway Keller. The Challenge of Facts: And Other Essays. New Haven: Yale University Press; [etc., etc.], 1914.
एमएलए (8वां संस्करण) प्रशस्ति पत्रSumner, William Graham, और Albert Galloway Keller. The Challenge of Facts: And Other Essays. Yale University Press; [etc., etc.], 1914.
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